Two invalid genera in the family Bythinellidae Locard, 1893 (Caenogastropoda: Truncatelloidea)

Abstract

Within the genus Bythinella Moquin-Tandon, 1856, with about 250 nominal species, the separation of several genera would be helpful in understanding the phylogenetic relationships between these snails, but neither morphology nor molecular loci studied so far can be used to distinguish any natural taxon over the range of species within this genus. Apart from Bythinella there are two other genera listed in the Bythinellidae by WoRMS: Terrestribythinella Sitnikova, Starobogatov et Anistratenko, 1992, and Strandzhia Georgiev et Glöer, 2013. Considering the cytochrome c oxidase subunit I (COI) sequences, as well as poor morphological data, Terrestribythinella should be considered a junior subjective synonym of Bythinella. In the case of Strandzhia, both COI and 18S sequences studied by us, as well as morphology re-examined (misinterpretation of the penis morphology in the original description) clearly show the assignment of Strandzhia to the genus Grossuana Radoman, 1983, thus Strandzhia becomes a junior objective synonym of Grossuana.